An example of the switching system to which the present invention applies is described in U.S. Pat. No. 5,544,163, Expandable Telecommunications System, the contents of which are incorporated herein by reference. The switching system comprises a plurality of programmable switching nodes and host software that exercises supervisory control over the switching nodes. The hosts are typically implemented as software applications running as a personal computer to provide various supervisory functions. The switching nodes are interconnected by an internodal switching network. A second network termed the "host network," interconnects the switching nodes and the host computer for supervisory communications. Examples of the host supervisory applications include call setup and teardown applications and applications that perform various system monitoring and administrative functions.
In the above-referenced patent, a single system host computer communicates with the switching nodes and all messages from the switching nodes are sent to that computer. However, in some environments the host computer may be overloaded, for example, by a high frequency of call setup and teardown operations and by other functions that may be assigned by the system operator. Moreover various nodes or groups of nodes may be situated in widely separated geographic locations and communications between a single host computer and all of the switching nodes may be substantially more expensive than distribution of the host functions on a geographic basis.
To solve these problems, a prior system divides the supervisory host applications among multiple host computers. This takes care of the host computer overload problem as well as the problem with widely separated geographic locations. However, the host applications usually have different priorities, with applications that perform call setup and teardown functions requiring the highest priority in the switching nodes. The operators of the switching system may divide the supervisory host applications among multiple host computers based on the their priorities. For example, the operator may limit to one computer host applications that control and configure various switching node features or perform call setup and teardown functions. The lower priority host applications will then be placed on other computers. However, all messages received by the switching nodes have the same priority and since all hosts communicate with the switching nodes, the switching nodes in turn, process lower priority applications at the same priority level as higher priority applications. This is not a problem with a single host computer system since requests can then be sent to the switching nodes according to the priority levels of the requests.